The present invention relates to interface between a tape reel assembly of a data storage tape cartridge and a tape drive clutch. More particularly, it relates to an engagement feature configured to provide dominant surfaces for mating between teeth of a tape reel assembly and teeth of a tape drive clutch, thereby dictating consistent reel/clutch engagement.
Data storage tape cartridges have been used for decades in the computer, audio, and video fields. The data storage tape cartridge continues to be an extremely popular device for recording large volumes of information for subsequent retrieval and use.
A data storage tape cartridge generally consists of an outer shell or housing containing at least one tape reel assembly and a length of magnetic storage tape. The storage tape is wrapped about a hub portion of the tape reel assembly and is driven through a defined tape path by a driving system. The housing normally includes a separate cover and base, the combination of which forms an opening (or window) at a forward portion thereof for allowing access to the storage tape by a read/write head upon insertion of the data storage tape cartridge into a tape drive. This interaction between storage tape and head may take place within the housing (for example, with a mid-tape load design), or the storage tape may be directed away from the housing to an adjacent area at which the read/write head is located (for example, with a helical drive design or a leader block design). Where the tape cartridge/drive system is designed to direct the storage tape away from the housing, the data storage tape cartridge normally includes a single tape reel assembly. Conversely, where the tape cartridge/drive system is configured to provide head/storage tape interaction within or very near the housing, a two- or dual-tape reel assembly configuration is typically employed.
Regardless of the number of tape reel assemblies associated with a particular data storage tape cartridge, the tape reel assembly itself is generally comprised of three basic components: namely, an upper flange, a lower flange, and a hub. The hub forms an outer, tape-winding surface about which the storage tape is wound. The flanges are disposed at opposite ends of the hub and are spaced to approximate the height of the storage tape. Finally, the tape reel assembly is adapted to be engaged by a drive clutch upon insertion into a tape drive, with the drive clutch causing the tape reel assembly to rotate in a desired fashion.
The well-accepted technique for facilitating interaction between the tape reel assembly and drive clutch is known as a xe2x80x9cpoker chipxe2x80x9d design whereby both the drive clutch and the tape reel assembly employ multiple, circularly arranged teeth designed to mate with one another. When mated, these teeth act both to locate the tape reel assembly at a center of the tape path, and to transmit torque from the tape drive motor/clutch to the tape reel assembly. To this end, one typical tooth design entails sixty teeth on both the tape reel assembly and drive clutch. As used throughout this specification, the tape reel assembly teeth situated to interact with the tape drive are referred to as xe2x80x9ctape reel teethxe2x80x9d or xe2x80x9creel teethxe2x80x9d, whereas the corresponding tape drive/clutch teeth are referred to as xe2x80x9cdrive clutch teethxe2x80x9d or xe2x80x9cdrive teethxe2x80x9d.
Regardless of the number of teeth, upon insertion of the tape cartridge into the drive, the tape reel assembly is generally aligned with the drive clutch. The tape reel assembly is then maneuvered toward the drive clutch (and/or the drive clutch moved toward the tape reel) such that the drive clutch teeth are guided into meshed engagement with the reel teeth. This meshed relationship facilitates rotation of the tape reel by the drive clutch. At any one point in time, however, only three of the tape reel teeth are in true contact with the drive clutch teeth, as a plane of interface can only be defined by three points. Unfortunately, it is virtually impossible with current tape reel assembly designs to predict or dictate which three reel teeth will define the interface plane due to their preferred, uniform nature. As a point of reference, tape reel assembly components, including the reel teeth, are plastic molded parts. Molding imperfections in the surface of the tape reel teeth, systematic deviations in angular spacing of the teeth due to an off-centered gate location and/or mold cooling profile, trapped debris and/or tooth damage due to wear all contribute to defining which three teeth on the tape reel actually contact/engage the drive clutch/teeth. As a result, when a cartridge is ejected and then re-inserted into a drive, a different set of three teeth will almost certainly mate with the drive clutch teeth, thus changing both the elevation and wobble of the tape reel assembly with each re-insertion. Further, if the three reel teeth that ultimately contact the drive clutch teeth are not evenly distributed around a center of the tape reel assembly, the tape reel assembly can rock or wobble on the drive clutch during use.
The above-described inherent inconsistencies in tape reel/drive clutch interface may lead to operation errors. To this end, a study was performed to estimate tape reel assembly wobble and elevation error as a function of angular error in the tape reel teeth. This analysis revealed that as little as ten minutes of angular error in the tape reel teeth can result in up to 35 mils of vertical run-out at the outer diameter of a xe2x80x9cstandardxe2x80x9d hub flange, and up to 14 mils of elevation error. In light of the continued evolution of storage tape technology toward increasingly smaller track widths, these deviations may present distinct opportunities for performance errors.
Data storage tape cartridges are important tools used to maintain vast amounts of information. As the cartridge and drive components continue to evolve, alignment deviations/inconsistencies between the tape reel assembly and drive clutch are less tolerable. Therefore, a need exists for a tape reel or drive clutch configured to consistently dictate the points of contact between tape reel teeth and drive clutch teeth.
One aspect of the present invention relates to a tape reel assembly for a data storage tape cartridge. The tape reel assembly includes a hub, opposing upper and lower flanges, a plurality of reel teeth, and three engagement features. The hub defines a tape-winding surface. The opposing upper and lower flanges extend in a radial fashion from opposing sides of the hub, respectively. The plurality of reel teeth extend axially outwardly relative to the hub. The reel teeth are circularly arranged for interacting with corresponding teeth of a drive clutch. Finally, the three engagement features are equidistantly spaced within the reel teeth. In this regard, the engagement features are each configured to provide a dominant mating surface relative to surfaces of the plurality of reel teeth. With this configuration, the three engagement features consistently mate with teeth of a tape drive clutch. During use, as the drive clutch is directed into engagement with the tape reel assembly, the three engagement features dictate the plane of contact between the tape reel assembly and the drive clutch, with the reel teeth serving as general guide surfaces that facilitate this interaction. In other words, the three engagement features always mate with the drive clutch teeth, thus defining both the elevation and wobble of the tape reel irrespective of insertion position. In one preferred embodiment, the engagement features are pronounced reel teeth, having a height or axial extension greater than that of the remaining reel teeth. In another preferred embodiment, the engagement features are provided in the form of a reduced-sized valley between two adjacent reel teeth. In particular, with this one preferred embodiment, the plurality of reel teeth define a plurality of valleys, with each valley being generated between two adjacent teeth. The reduced-sized valley associated with the engagement features are smaller in terms of depth or width than the remaining valleys, again dictating that ultimate drive clutch teeth contact occur at the point of these engagement features.
Another aspect of the present invention relates to a data storage tape cartridge including a housing, at least one tape reel assembly, and a storage tape. The housing includes a base and a cover that combine to define an enclosed space. The base forms at least one tape reel opening. The at least one tape reel assembly includes a hub, opposing upper and lower flanges, a plurality of reel teeth and three engagement features. The hub defines a tape-winding surface. The opposing upper and lower flanges extend in a radial fashion from opposing sides of the hub, respectively. The plurality of reel teeth extend axially outwardly relative to the hub, and are circularly arranged. The three engagement features are equidistantly spaced within the reel teeth. In this regard, the at least one tape reel assembly is disposed within the housing such that the reel teeth and engagement features are accessible through the tape reel opening. Finally, the storage tape is wound about the tape-winding surface of the hub. The engagement features are each configured to provide a dominant mating surface relative to surfaces of the plurality of reel teeth. This configuration dictates that upon insertion of the data storage tape cartridge into a tape drive, the teeth of an associated drive clutch will consistently mate only with the engagement features, thereby ensuring tape reel assembly/drive clutch stability.
Yet another aspect of the present invention relates to a tape reel assembly for a data storage tape cartridge. The tape reel assembly includes a hub, opposing upper and lower flanges, and a plurality of reel teeth. The hub defines a tape-winding surface. The opposing upper and lower flange extend in a radial fashion from opposing sides of the hub, respectively. Finally, the plurality of reel teeth extend axially outwardly relative to the hub. The reel teeth are circularly arranged, and each reel tooth is defined by opposing side surfaces. With this in mind, the plurality of reel teeth include a plurality of guide teeth and three equidistantly spaced dominant tooth arrangements. The opposing side surfaces of the guide teeth each have corresponding lengths and angular orientations. In contrast, the dominant tooth arrangements each include at least one dominant tooth, at least one opposing side surface of which has a dominant length and/or dominant angular orientation that differs from the length and/or angular orientation of the guide teeth. With this configuration, then, contact between teeth of a drive clutch and the tape reel assembly occurs only at the dominant tooth arrangements. In one preferred embodiment, the dominant tooth arrangements are configured to prevent the drive clutch teeth from engaging the guide teeth.
Yet another aspect of the present invention relates to a tape drive clutch of a tape drive mechanism for operatively engaging tape reel teeth of a data storage tape cartridge. The tape drive clutch includes a plurality of drive clutch teeth and three, equidistantly spaced engagement features. The engagement features are provided within the drive clutch teeth and provide dominant mating surfaces relative to surfaces of the drive clutch teeth. With this configuration, the three engagement features consistently mate with tape reel teeth of the data storage tape cartridge, dictating a plane of contact between the drive clutch and the tape reel. In one preferred embodiment, the engagement features are dominant drive clutch teeth; in another preferred embodiment, the engagement features are dominant valleys.